Lamp failure detection and change device

ABSTRACT

A projector which has a device for automatically replacing an expired main lamp with a spare lamp. The main lamp and the spare lamp are socketed in a lamp-changing mechanism which is operated in response to the operation of a lamp failure detector. The detector radiantly senses the failure of the main lamp and automatically activates the lamp-changing mechanism which will remove the main lamp from the focus position, advance the spare lamp into the focus position, and energize the spare lamp.

United States-Patent Inventor Jack P. Blomgren Maplewood, Minn.

Jan. 10, 1969 May 4, 1971 Minnesota Mining and Manufacturing Company St.Paul, Minn.

App]. No. Filed Patented Assignee LAMP FAILURE DETECTION AND CHANGEDEVICE 5 Claims, 3 Drawing Figs.

US. Cl 315/88, 240/371, 315/151, 352/198 Int. Cl ..F21v 19/04, H05h37/04 Field of Search 315/86, 87, 88, 89, 90, 93, 149, 159; 240/37,37.1; 352/198; 353/85, 87

[56] References Cited UNITED STATES PATENTS 1,830,537 1 H1931 Frappieret al. 240/37.l 1,842,963 l/1932 Day 240/37.l 2,892,966 6/1959 Smyth315/89 3,146,375 8/1964 Campbell 315/89 Primary Examiner-Roy LakeAssistant Examiner-E. R. LaRoche Attorney-Kinney, Alexander, Sell,Steldt & Delahunt ABSTRACT: A projector which has a device forautomatically replacing an expired main lamp with a spare lamp. The mainlamp and the spare lamp are socketed in a lamp-changing mechanism whichis operated in response to the operation of a lamp failure detector. Thedetector radiantly senses the failure of the main lamp and automaticallyactivates the lamp-changing mechanism which will remove the main lampfrom the focus position, advance the spare lamp into the focus position,and energize the spare lamp.

LAMP FAILURE DETECTION AND CHANGE DEVICE BACKGROUND OF THE INVENTIONEducators, instructors and lecturers of all types have adopted the useof light-projecting devices such as slide projectors, movie projectors,and overhead projectors to dramatically and effectively present theirsubject matter to an audience. While it is desirable to be able tointerrupt the picture series for the purpose of discussion andexplanation or to point out certain objects in the picture on thescreen, it is obviously undesirable to experience an unplannedexasperating interruption of the visually aided lecture by having theprojectors lamp burn out.

SUMMARY OF THE INVENTION The. present invention relates to a projectorhaving a device for detecting the failure of the main lamp andautomatically replacing the properly positioned expired main lamp withthe spare lamp, and in one aspect to a lamp failure detector havingenergy-sensing means and release means for activating the movement ofthe lamp-changing mechanism for moving the main lamp out of the focusposition, moving the spare lamp into the focus position, and supplyingenergy to the spare lamp for continuation of the presentation with theminimum of interruption.

This device, therefore, detects the failure of the main lamp within alight-projecting device such as a slide projector, movie projector oroverhead projector and automatically replaces the expired main lamp witha spare lamp for continuation of the program with a minimum ofinterruption.

Other uses and many of the attendant advantages of this invention willbe readily understood and appreciated as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawing in which likenumerals designate like parts throughout the FIGS. and detaileddescription and wherein;

FIG. 1 is a perspective view, partly in section, of an overheadprojector utilizing the teachings of the present invention;

FIG. 2 is a perspective view, partly in section, of a portion of thelamp changing mechanism; and

' FIG. 3 is a wiring diagram, partially in pictorial form, of the lampfailure detector.

In the drawing and description of the embodiment of the inventionillustrated in FIG. 1, the end of the projector shown at the right willbe referred to as the "front of the projector and the opposite end willbe referred to as the "back." The portion of themachine which is in theuppermost in FIG. 1 comprises the upper.portion of the machine and theopposite portion therefrom is called the bottom" of the machine. Themain lamp 40, as shown in FIGS. 1 and 2, is located in the focusposition which is the proper focal length from the condensing lens ofthe Fresnel type and along the optical centerline" of the projector.

Referring now to the embodiment shown in FIG. 1 there is shown anoverhead projector generally designated illustrative of the teachings ofthe invention, comprising a projection head 12 vertically supported bythe lower boxlike case or base structure 14. The base structure 14further comprises a stage glass 16 on which the transparency is placed,Fresnel lens 18 detector 35 for sensing and'reacting to the failure ofthe main lamp 40.

The lamp-changing mechanism 34, as shown in FIGS. l and 2. comprises arotatable lamp support 36, an actuation means including a resilientspring 38 as biased in FIG. I, and a first electrical means includingelectrical contacts 39 and 41 for electrically connecting the main lamp40 and the spare lamp 42, respectively, to a l20-volt AC source via theswitch 22. The rotatable support 36, which is pivotably mounted onpivots 43, comprises a base 44 to which the contacts 39 and 41 aremechanically secured, a rear vertical wall 46 and a front vertical wall48 having an arm 50 operably connected to the spring 38 and a step 52 tooperably engage the release means 60. The main lamp 40 and the sparelamp 42 of the projector, as shown in FIGS. 1 and 2, are detachablysocketed to one or the other of the walls 46 and 48 or as illustrated tothe rear wall 46 and the front wall 48, respectively, of the lampsupport 36. The main lamp 40, as shown in FIGS. 1 and 2, is located inthe focus position of the projector and upon rotation of the mechanism34, under the bias of spring 38, the main lamp 40 will be moved out. ofthe focus position and the mechanism 34 will rotate until positionedagainst a stop member (not shown) which will locate the spare lamp 42 inthe focus position. Upon movement of the lamp-changing mechanism 34,contacts 39 will move away from the base contacts 45 secured to theframe 33 and contacts 40 will engage contacts 45 to electrically closethe circuit to the spare lamp and thus provide illumination from thespare lamp 42.

The lamp failure detector 35, as pictorially shown in FIG. 3, comprisesa single-pole switch 22 to provide electrical energy to the projector 10from the l20-volt AC source, a time delay means 56, an energy-sensingmeans 58, and a release means 60.

The energy-sensing means 58 is located near the main lamp 40 to detectand react to the radiant energy from the filament of the lamp 40 and theabsence of radiant energy from the filament of the lamp 40. Theenergy-sensing means illustrated includes a first bimetal bar 62mechanically secured to the base which will open the contacts 63 inreaction to heat energy from the lamp 40. Thus, during normal operationof the projector 10 in which the main lamp 40 is illuminating the bar 62will be bent to provide open contacts 63. Upon interruption of the heatfrom the lamp 40, the bar 62 will mechanically bend to close thecontacts 63 and complete a portion of the electrical circuit through therelease means '60. When the projector 10 is initially turned on and thecontacts 63 are closed, however, the electrical circuit through theenergy sensing means and the release means should be electrically opento prevent erroneous movement of the lamp-changing mechanism 34. Thecircuit may be maintained in an open condition by the use of a manualswitch (not shown) or may be automatically opened and closed by a timedelay means 56.

The time delay means 56 includes a second bimetal bar 64 to open andclose the contacts 65 in response to heat energy provided by a secondelectrical means 61 including heater wires 66 encircling the bar 64.Upon closing of the switch 22 the heater wires 66 electrically connectedin parallel with the lamp 40 will provide heat energy to the secondbimetal bar 64. Thus heat will cause the bar 64 to mechanically bend andelectrically close the contacts 65 within a predetermined time periodafter the switch 22 has been closed. Immediately after the switch 22 isclosed the main lamp is illuminated which provides heat to the firstbimetal bar 62 and the heater wires 66 provide heat to the secondbimetal bar 64. The first bimetal bar 62 of the energy-sensing means 58reacts more quickly,

than bar 64, to open the contacts 63 before the contacts 65 are closedto prevent erroneous movement of the mechanism 34. If the main lamp 40expired after the projector 10 had been turned off, as for example bythe filament breaking, then upon closing of switch 22 the energy-sensingmeans 58'will not receive any heat and the contacts 63 will remainclosed and upon the closing of contacts 65 the release means 60 will beenergized to activate the movement of the mechanism 34. Also, if themain lamp expires during operation of the projector 10 the contacts 65will have been closed and with the absence of heat the contacts 63 ofthe energy-sensing means 58 will close to energize the release means 60.

The release means 60 includes a third bimetal bar 68 to engage andrelease the step 52 in response to heat energy provided by a thirdelectrical means 69 including heater wires 70 encircling the bar 68.when contacts 63, 65 are closed and electrical energy is providedthrough the heater wires 70, this energy will provide heat tomechanically bend the bar 68 to an indicating lamp 72 to notify theoperator that the spare I lamp is in operation.

While the energy-sensing means 58 is illustrated as the above-mentionedbimetal bar responsive to the radiant energy from the main lampfilament. it could have the form of a photocell or other similarapparatus to sense light rays or other forms of electromagnetic energyfrom the main lamp 40 and thus activate the release means 60 in responseto the absence of energy form the main lamp 40.

lclaim:

l. A device having particular utility in a light projecting system fordetecting the failure of a main lamp and automatically replacing theexpired main lamp in the optical system with a spare lamp, said devicecomprising in combination:

l.aframe;

2. a lamp-changing mechanism having:

a. a lamp support mounted on said frame for movement from a first setposition to a second set position;

b. a main lamp and a spare lamp mounted on said lamp support, toposition said main lamp in a predetermined position when said support isin said first set position and to position said spare lamp in thepredetermined position when said support is in said second set position;

0. actuation means operably connected to said support for moving saidlamp support between said first set position and said second setposition; d. first electrical means on said support for electricallyconnecting the main lamp to a source of electrical energy in said firstset position and for connecting said spare lamp to a said source uponmovement of said support to said second set position;

3. a lamp failure detector having:

a. energy sensing means for detecting and reacting to the interruptionof radiant energy from said main lamp;

b. release means operatively responsive to the" reaction of saidenergy-sensing means for activating said actuation means; and

c. a time delay means operably connected to said energy sensing meansfor electrically connecting said energy sensing means to a source ofelectrical energy after a short period of time has elapsed from initialenergization of said device.

2. The device according to claim 1 wherein said energysensing meansincludes a first bimetal means adjacent the main lamp for mechanicallyreacting to the interruption of energy through said main lamp toelectrically connect said release means to the source of electricalenergy.

3. The device according to claim 2 wherein said time delay meansincludes:

l. a second electrical means operatively connected to a source ofelectrical energy for providing heat energy; and

2. a second bimetal means adjacent said second electrical means formechanically reacting to the heat energy in said second electrical meansto electrically connect said energy-sensing means to a source ofelectrical energy after a short period of time has elapsed from initialenergization of said device.

4. The device according to claim 3 wherein said release means includes:

1. a third electrical means operatively connected to said ener g -sensin means for providin heat energy; and 2. a thir bimeta means adacent sat third electrical means for mechanically reacting to the heatenergy in said third electrical means to activate said actuation means.5. The device according to claim 4 further including means responsive tothe movement of said support for providing an indication to the operatorthat the spare lamp is in operation.

1. A device having particular utility in a light projecting system fordetecting the failure of a main lamp and automatically replacing theexpired main lamp in the optical system with a spare lamp, said devicecomprising in combination:
 1. a frame;
 2. a lamp-changing mechanismhaving: a. a lamp support mounted on said frame for movement from afirst set position to a second set position; b. a main lamp and a sparelamp mounted on said lamp support, to position said main lamp in apredetermined position when said support is in said first set positionand to position said spare lamp in the predetermined position when saidsupport is in said second set position; c. actuation means operablyconnected to said support for moving said lamp support between saidfirst set position and said second set position; d. first electricalmeans on said support for electrically connecting the main lamp to asource of electrical energy in said first set position and forconnecting said spare lamp to a said source upon movement of saidsupport to said second set position;
 3. a lamp failure detector having:a. energy sensing means for detecting and reacting to the interruptionof radiant energy from said main lamp; b. release means operativelyresponsive to the reaction of said energy-sensing means for activatingsaid actuation means; and c. a time delay means operably connected tosaid energy sensing means for electrically connecTing said energysensing means to a source of electrical energy after a short period oftime has elapsed from initial energization of said device.
 2. a thirdbimetal means adjacent said third electrical means for mechanicallyreacting to the heat energy in said third electrical means to activatesaid actuation means.
 2. a second bimetal means adjacent said secondelectrical means for mechanically reacting to the heat energy in saidsecond electrical means to electrically connect said energy-sensingmeans to a source of electrical energy after a short period of time haselapsed from initial energization of said device.
 2. The deviceaccording to claim 1 wherein said energy-sensing means includes a firstbimetal means adjacent the main lamp for mechanically reacting to theinterruption of energy through said main lamp to electrically connectsaid release means to the source of electrical energy.
 2. alamp-changing mechanism having: a. a lamp support mounted on said framefor movement from a first set position to a second set position; b. amain lamp and a spare lamp mounted on said lamp support, to positionsaid main lamp in a predetermined position when said support is in saidfirst set position and to position said spare lamp in the predeterminedposition when said support is in said second set position; c. actuationmeans operably connected to said support for moving said lamp supportbetween said first set position and said second set position; d. firstelectrical means on said support for electrically connecting the mainlamp to a source of electrical energy in said first set position and forconnecting said spare lamp to a said source upon movement of saidsupport to said second set position;
 3. a lamp failure detector having:a. energy sensing means for detecting and reacting to the interruptionof radiant energy from said main lamp; b. release means operativelyresponsive to the reaction of said energy-sensing means for activatingsaid actuation means; and c. a time delay means operably connected tosaid energy sensing means for electrically connecTing said energysensing means to a source of electrical energy after a short period oftime has elapsed from initial energization of said device.
 3. The deviceaccording to claim 2 wherein said time delay means includes:
 4. Thedevice according to claim 3 wherein said release means includes:
 5. Thedevice according to claim 4 further including means responsive to themovement of said support for providing an indication to the operatorthat the spare lamp is in operation.